Crosstalk suppression for extrinsic fiber F-P sensor array using wavelength diversity demodulation

Abstract

Extrinsic fiber-optic Fabry–Perot (F-P) hydrophones are key devices for underwater acoustic detection. Current multiplexing techniques for F-P cavity sensors face significant limitations: wavelength-division multiplexed (WDM) arrays are prone to optical crosstalk, which degrades multiplexing capacity and detection accuracy, hindering practical deployment of large-scale sensor networks. To address crosstalk suppression in WDM-based extrinsic fiber F-P hydrophone arrays, this paper proposes a white-light interference-based multi-wavelength five-step phase-shifting diversity demodulation method. The scheme obtains reflection spectra via white-light interference, removes spectral envelopes and corrects signals using an extremum algorithm, extracts demodulation parameters via ellipse fitting, and achieves orthogonal demodulation and phase recovery through multi-wavelength diversity averaging. Experimental and numerical results for a two-channel WDM array demonstrate that the proposed method outperforms conventional single-wavelength five-step phase-shifting demodulation, yielding crosstalk suppression above 30 dB, comparable to high-end engineering-grade demodulators. In experiments, fundamental-frequency crosstalk suppression reaches 33.7 dB with 15.8 dB total harmonic distortion reduction; simulations achieve 38.8 dB and 16.5 dB, respectively. The influence of signal amplitude on crosstalk suppression is also analyzed. The method effectively mitigates WDM crosstalk bottlenecks, enabling large-scale extrinsic fiber F-P hydrophone arrays, and is promising for underwater dynamic acoustic sensing and large-scale fiber-optic sensor applications.